Production of hydrocarbon lead compounds



United States Patent one 3,522,156 Patented July 28, 1970 US. Cl. 204-59 6 Claims ABSTRACT OF THE DISCLOSURE Production of tetravalent vinyl lead compounds by electrolyzing in an electrolytic cell having a lead anode a liquid composition which is a complex of a vinylic magnesium halide and a cyclic mono ether capable of complexing with the halide.

This application relates to a process for the production of lead compounds having vinylic groups attached to the lead.

This application is a continuation-in-part of my copending application Ser. No. 377,097, filed June 22, 1964, now US. Pat. 3,431,185, and entitled, Hydrocarbon Lead Production, and Ser. No. 377,093, filed June 22, 1964, now abandoned, and entitled, Production of Hydrocarbon Lead Compounds.

The preparation of vinyllead compounds has been disclosed in US. Pat. 3,071,607, patented Jan. 1, 1963. According to this patent the vinyllead compounds may be produced for example by reacting a vinyl Grignard reagent with the appropriate lead salt. However, such a process has certain disadvantages such as the relatively low yields obtained. Further, the free lead produced by such a reaction will not react with additional quantities of vinyl Grignard reagent and thus it must be recovered. It is an object of this invention to provide an improved process for the preparation of lead compounds having at least one vinylic group attached to the lead. It is an additional object of this invention to directly produce an organolead composition suitable for improved antiknock compositions. Another object is to provide an electrolysis process wherein the electrolyte has improved conductivity. These and other objects will be apparent in the description which follows.

According to this invention tetravalent vinylic lead compounds may be produced by electrolyzing in an electrolytic cell having a lead anode, a liquid composition comprising a vinylic Grignard reagent (i.e., a vinylic magnesium halide). The anode of the electrolytic cell supplies the lead of the organolead product. The cathode may be either lead or other suitable material such as stainless steel.

The preparation of lead compounds by the electrolysis, with a lead anode, of a Grignard reagent has been disclosed in the prior art. US. Pat. 3,007,857 and US. Pat. 3,007,858, both issued Nov. 7, 1961, disclose the electrolysis of a Grignard reagent. However, in both of these patents the Grignard reagents employed are alkyl Grignard reagents. One of the serious drawbacks of the processes disclosed in US. 3,007,857 and US. 3,007,858 is the low conductivity of the electrolytes. In any electrolysis process the conductivity of the electrolyte is a critical factor and if the conductivity is too low the process is uneconomical. On the other hand, electrolytes of high conductivity diminish the cost of current for operation of the electrolytic cell.

It has now been discovered that electrolytes comprising Grignard reagents having at least one vinylic radical possess a considerably higher conductivity than those not having the vinylic radical. Accordingly it has been discovered that electrolytes comprising vinylic Grignard compounds may be electrolyzed with low voltage requirements even in the absence of added electrolytes.

One of the preferred embodiments of this invention is the use of certain cyclic ethers in the electrolyte during the electrolysis of the vinylic Grignard reagent. These cyclic ethers are mono ethers which form complexes with the vinylic Grignard reagent. The cyclic ethers will be described in greater detail below. Examples of these cyclic mono ethers are tetrahydrofuran and tetrahydropyran. The cyclic ethers are preferred because of overall improved results including higher yields.

The process of this invention may be more completely understood and illustrated by the following examples. All parts are by Weight unless expressed otherwise.

EXAMPLE I The electrolytic cell used in these tests has a 29 mm. by 200 mm. Pyrex test tube fitted with a stopper having a %-inch glass T for charging the electrolyte or for connection to a gas burette fitted with mercury for collecting and measuring gases evolved. When gas was not being collected the side arm of the glass T was connected to a nitrogen bubbler for maintaining an inert atmosphere in the cell. Two copper wires for the electrical leads were fitted tightly through holes in the stopper. The cathode was a stainless steel rectangular sheet which was about 2 cm. wide, 10 cm. long and about ;-inch thick. The cathode was sandwiched between two lead anode sheets of approximately the same size as the cathode. Teflon spacers held the electrodes about 0.5 cm. apart. Electrical direct current (DC) was supplied for the test by a battery charger operating off regular -volt AC supply line and voltage control was obtained by a rheostat on the battery charger. The current was measured by an ammeter and by a copper coulometer.

The electrolyte comprised vinyl magnesium chloride in a solution of tetrahydroguran (THF). The electrolyte solution measured 2.15 moles of Mg++ per liter of solution and 2.16 equivalents of Clion per liter of solution. The gas evolved upon hydrolysis was 1.20 milliequivalents per ml.

The electrolytic cell was charged with 50 ml. of the vinyl magnesium chloride-THF electrolyte solution. During approximately a 4-hour run the voltage was maintained at from about 1.7 to 3.9 volts at an amperage of 200 milliamps. A gas sample was analyzed by vapor phase chromatogram and it was determined that the product was vinyl lead compound.

EXAMPLE II The apparatus and procedure of Example I is utilized with the exception that the electrolyte comprises vinyl magnesium chloride and tetrahydropyran instead of tetrahydrofuran. After a 6-hour run at an average voltage of 2.5 volts and an amperage of 200 milliamps tetravinyl lead is produced in good yields.

EXAMPLE III Example I is repeated with the exception that the same molar equivalent of vinyl magnesium bromide in tetrahydrofuran is substituted for the vinyl magnesium chloride of Example I. Substantially equivalent results are obtained as those in Example I.

EXAMPLE IV Vinyl magnesium chloride was prepared by the reaction of magnesium and vinyl chloride. Magnesium chips, 121.6 g., were reacted in 1,075 g. of tetrahydrofuran with 396 g. of vinyl chloride. The reaction product was cooled and unreacted vinyl chloride was vented. The product solution, 1300 ml., was decanted and 500 ml. of tetrahydrofuran was added to extract the residue. Most of the residue went into solution, which was then decanted and added to the product solution giving it a total of 1900 ml. Aliquots of this product solution indicated it was 2.64 molar with respect to magnesium and 2.74 molar with respect to chloride ions. The product solution (25 ml. portions equivalent to 67.25 millimols of vinyl magnesium chloride) is used as the electrolyte.

During a 4-hour run the average voltage is about 3.0 and the current amperage is about 175 milliamps. The product, tetravinyl lead, is determined by vapor phase chromatogram.

EXAMPLE V Example I is repeated with the exception that 1-propenyl magnesium chloride is substituted for the vinyl magnesium chloride of Example I and 4-methoxy tetrahydrofuran is substituted for the tetrahydrofuran. The product, tetra l-propenyl lead, is determined by vapor phase chromatography.

Similar results are obtained when Example I is repeated using 2-methyl-l-butenyl magnesium chloride instead of the vinyl magnesium chloride.

As pointed out, the preferred electrolytes will comprise a vinylic magnesium halide (i.e., the vinylic Grignard reagent) and certain cyclic mono ethers. The vinylic magnesium halide and the cyclic mono ether form a complex. By the term vinylic magnesium halide is meant l-alkenyl compounds of the formula wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine, and R and R are the same or different hydrocarbon radicals, hydrocarbonoxy radicals or hydrogen, such as those selected from the group consisting of hydrogen, alkyl, alkoxy, aryl, aralkyl, alkaryl, aryloxy and mixtures thereof. The aryl radicals suitably contain a single benzene ring with the radicals being such as the phenoxy radical, phenyl radical and the mono-, diand tri-aliphatic substituted phenyl or phenoxy radicals. The vinylic magnesium chloride compounds will have from 2 to 20 carbon atoms. Examples of vinylic magnesium chloride compounds are vinyl magnesium chloride, l-propenyl magnesium chloride, 1- hexenyl magnesium chloride, 2-ethyl l-hexenyl magnesium chloride, vinyl magnesium bromide, Z-phenyl 1- ethenyl magnesium chloride, 2-phenoxy l-ethenyl magnesium chloride, 2-tolyl l-ethenyl magnesium chloride, cyclohexene-l-yl-l magnesium chloride, mixtures thereof and the like. The preferred vinylic magnesium halide is vinyl magnesium chloride because of the overall economic advantage and the superior results obtained. The vinylic magnesium halides of the formula R @CHMgX may be produced in conventional manner as illustrated by the examples.

The preferred electrolyte will be a complex of the vinylic magnesium halide compound and cyclic ethers capable of complexing with the vinylic magnesium halide compound. Suitable cyclic ethers of the complex are mono ethers such as those having the formula wherein R is an unsubstituted alkylene radical, R is selected from the group consisting of an ethylene radical, an ethylenically unsaturated divalent hydrocarbon radical, CHA and mixtures thereof; Z is selected from the group consisting of a methylene radical, NA and mixtures thereof, and A is an aliphatic radical of from 1 to carbon atoms. When Z is NR, the ring will contain 6 members and Z and O (i.e., the oxygen atom) will be 1,4 with respect to each other. The cyclic ethers will suitably contain up to 20 carbon atoms. Generally, there will be at least one hydrogen atom attached to each carbon atom in the ring. The cyclic ether may be substituted with radicals which will not react with the vinylic magnesium chloride compound. Suitable substituents are alkyl radicals such as ethyl, aryl radicals such as phenyl, alkoxy radicals such as methoxy, and aryloxy radicals such as toloxy. The number of carbon atoms in the substituted radicals will be from one to 12, preferably from one to 8. Preferably, the cyclic ethers will have from 5 to 6 atoms in the ring structure. The cyclic ethers will be constituted only of elements of the group consisting of carbon, hydrogen, oxygen and nitrogen. Suitable cyclic ethers are tetrahydrofuran, 3-ethyl tetrahydrofuran, 2-(o-toloxy) tetrahydrofuran, N-methyl morpholine, the methyl ether of tetrahydrofurfuryl alcohol, 3-phenoxy-tetrahydrofuran, 4-ethoxy-tetrahydrofuran, 2,5- dihydrofuran, tetrahydropyran, 4-methoxy-tetrahydropyran, 2-ethoxy-3,4-dihydro-2H-pyran, mixtures thereof and the like.

The preferred cyclic ethers complexed with the vinylic magnesium halide are tetrahydrofuran and tetrahydropyran with tetrahydrofuran being especially preferred as high yields of the vinylic lead compounds are produced. The oxygen of the cyclic ether must be free to form a complex with the vinylic magnesium halide, consequently, the cyclic ethers employed should not have groups in the ring which would block the formation of a complex between the ring oxygen and the vinylic magnesium halide.

The cyclic ether should preferably be present in an amount of at least about one mole of cyclic ether per mole of vinylic magnesium halide and better results are generally obtained when the cyclic ether is present in an amount of greater than one mole per mol of vinylic magnesium halide. The upper limit of cyclic ether is not particularly critical but for economic reasons will not ordinarily exceed 4-or 5 moles of cyclic ether per mole of vinylic magnesium halide. A suitable range is from about .75 to 3.5 moles of cyclic ether per mole of vinylic magnesium halide. Solvents or diluents may be added to the complex. However, selection of the quantity and type of the solvent should be controlled in order that the production of the desired vinylic lead compounds be achieved. The cyclic ether will, for best results, constitute at least 75 mol percent of the total solvent and diluent present in the composition of the complex to be electrolyzed.

Other less suitable solvents are the aliphatic ethers and polyethers, tertiary amines, other organometallics, amides and substituted amides, and hydrocarbons, particularly the aromatic hydrocarbons. Examples of solvents are triisopropyl amine, toluene, xylene, and the like. Additional typical examples of suitable solvents are dialkylamides such as diethylamide and ethers, such as dimethyl ether, methylethyl ether, methyl-n-propyl ether, and mixtures of these. Suitable polyethers are ethylene glycol diethers, such as methylethyl, diethyl, ethylbutyl, and dibutyl; diethylene glycol ethers, such as dimethyl, diethyl, ethylbutyl and butyl lauryl; trimethylene glycol ethers, such as dimethyl, methylethyl; glycerol ethers, such as trimethyl, diethyl methyl, etc.; and cyclic diethers such as dioxane. Typical amines suitable for this inven tion include aliphatic and aromatic amines. Suitable tertiary amines (other than the preferred heterocyclic nitrogen compounds mentioned above) for use in this invention are trimethyl amine, dimethyl ethyl amine and tetramethyl ethylene diamine. Primary and secondary amines can also be used, such as methyl amine, dimethyl amine, etc. Mixtures of these enumerated solvents and the preferred cyclic mono ethers may be employed with advantage.

The lead anode can be pure lead or alloys thereof of varying shapes. Typical examples of alloy metals are bismuth, cadmium, antimony and copper. The lead or lead alloys can be coated or impregnated on a conductive metal, either metallic or nonmetallic, such as graphite. The lead anode may be replenished by lead shot or lead sheet, etc. The cathode can be any suitable conductive metal but is preferably one which does not alloy with the metal produced.

The voltage and amperage necessary for the reaction depend somewhat upon the particular cell being employed and the specific electrolyte. In general, not greater than 0.25 ampere/sq. cm. is employed. A preferred range is between 0.002 to 0.1 ampere/ sq. cm.

The cell employed may be of conventional design with one or more electrodes and cathodes. Provision should be made for the release of any gases evolved during the reaction. Also the cell should be suitable for operating under the pressure generated by the particular reactants at the temperature of reaction. Suitably the electrolytic solution will be anhydrous.

The temperature during electrolysis is not critical. It should be sufliciently high to give reasonable reaction rates but should not be above the decomposition temperaure of the organometallic reactants or the organolead products. Thus, the operating temperature of the reaction depends upon the particular organometallic compounds involved. In general, suitable temperatures are between about 30 C. and about 130 C., but temperatures from about to 100 C. are preferred to facilitate heat removal, for maximum current efiiciency and for best results. Higher temperatures can be employed when using organolead thermal stabilizers. In some instances considerable exothermic heat is generated and consequently a cooling medium may be desired to control the temperature.

About atmospheric pressure is normally employed, although subatrnospheric pressures are permissible. In some instances, supraatmospheric pressure is preferred, particularly when employing a relatively high temperature and a relatively volatile solvent or electrolyte. Also, a pressure of inert gas is sometimes desirable, for example, to assure anhydrous conditions. The pressure will generally be form about 0 to 500 p.s.i. with the range of about atmospheric (STP) to 250 p.s.i.g. being particularly suitable.

The vinylic lead products may also contain other organo groups such as alkyl groups by adding, e.g., an alkyl halide to the electrolyte during electrolysis. This subject matter is particularly claimed in my copending application Ser. No. 377,097, filed June 22, 1964, now US. Pat. 3,431,185, and entitled, Hydrocarbon Lead Production.

The products of this invention possess considerable utility. These compositions are soluble in hydrocarbons and are valuable as antiknock compositions for gasolines.

Other embodiments of this invention can be made without departing from the spirit and scope of this invention wherein R is an unsubstituted alkylene radical; R is selected from the group consisting of an ethylene radical, an ethylenically unsaturated divalent hydrocarbon radical, and a =CHA radical; Z is selected from the group consisting of a methylene radical, a =NA radical; and A is an aliphatic radical having from 1 to about 10 carbon atoms.

2. The process of claim 1 further characterized by Z being =NR and Z and 0 being 1,4 with respect to each other.

3. The process of claim 1 further characterized by the vinylic radical of said vinylic magnesium halide having from 2 to about 20 carbon atoms.

The process of claim 3 further characterized by said cyclic mono ether having from about 4 to about 6 carbon atoms in the ring structure.

5. The process of claim 3 further characterized by said complex being present in a solvent solution.

6. The process of claim 5 further characterized by said cyclic mono ether being present in a concentration of at least mol. percent of the solvent present in said solvent solution.

References Cited UNITED STATES PATENTS 2,535,193 12/1950 Calingert et al. 20459 XR 3,116,308 12/ 1963 Linsk 204--59 3,155,602 11/1964 Linsk et al. 20459 3,156,716 11/1964 Rarnsden et a1 260-437 FOREIGN PATENTS 824,944 12/ 1959 Great Britain.

JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner US. Cl. X.R. 20472 

